In a series entitled “50 Years Ago This Week,” TIME magazine investigates its headlines of the same dates a half-century ago. Earlier this month, the publication focused on the cover story of the week of April 7, 1967—featuring the wonders of the birth control pill.

In fewer than ten years on the market, the oral contraceptive had, the 1967 cover story asserted, “changed and liberated the sex and family life of a large and still growing segment of the U.S. population.” This miracle drug was poised to address overpopulation concerns rampant during the time, and so “go far toward eliminating hunger, want and ignorance.” TIME believes that “the story reflects a moment in time when concern over population control and the rise of women in the workforce converged with the available science to provide the right solution at the right time.”

But 50 years later, research is shedding light on some of the more unpleasant side effects of hormonal contraceptives, research that may indicate that “the right solution at the right time” may have been not so right, after all.

Almost six decades after the FDA approved the Pill—the oral contraceptive—progressives are still proclaiming its liberating virtues loudly. Perhaps they feel compelled to speak loudly in order to drown out the sobering reports on the harmful side effects of their chemical emancipator. Still, those reports do keep drifting in. This latest report—published by researchers at Kermanshah University of Medical Sciences in Iran—concludes that women who use the Pill face a risk of breast cancer more than half again higher than that faced by women who do not.

The authors of the new study decided to investigate the relationship between oral contraceptives and breast cancer for two compelling reasons. First, breast cancer is currently among the most common causes of death among women: worldwide, about one and a half million women are diagnosed with the disease each year, and nearly half a million die as its victims. Worse, discernible trends in available evidence indicate that “the next 20 years will witness considerable increase in incidence of the disease.” Though the disease strikes women in all lands, epidemiologists find a “high incidence . . . [of the disease] in more developed countries and low incidence in undeveloped countries.”

Given that women in economically developed countries use the Pill much more than women in undeveloped countries, it is not surprising that some researchers have hypothetically identified oral contraceptives as carcinogens. But the studies on the matter to date have returned inconsistent results: “Some findings have shown that taking these pills does not have a significant effect in increasing the risk of breast cancer,” the authors of the new study remark, “while others have confirmed the carcinogenic effect of these products.” Themselves located in a fast-modernizing country where the incidence of breast cancer “is expected to increase drastically . . . over the next decades,” the authors of the new study consider it a matter of some urgency to resolve the ambiguity in the “contradictory findings” on the linkage between oral contraceptives and breast cancer.

As a meta-analysis, this new Iranian study actually draws together and summarizes the results of 26 studies, all published between 2000 and 2015. A total of 46,260 Iranian women were involved in these studies, 24 of which were case-control studies, while 2 were population-based studies.

After careful analysis, the authors of the new study calculate that, collectively, the 26 studies yield an “Overall estimate of O[dds]R[atio] for the effect of oral contraceptive pills on breast cancer [as] 1.521 (CI = 1.25–1.85).” In other words, these studies reveal that among Iranian women, “using [contraceptive] pills increased the risk of breast cancer . . . 1.52 times.”

In explaining their findings, the Kermanshah scholars reason that oral contraceptives—“mainly composed of estrogen and progesterone”—may cause breast cancer directly by artificially increasing estrogen levels in the body. The researchers further argue that since elevated estrogen levels are associated with weight gain and since a number of studies have limned “a relationship between obesity and breast cancer,” use of oral contraceptives “directly leads to overweight and indirectly to breast cancer.”

Regardless of how contraceptives expose women to increased risk of breast cancer, the researchers worry about the magnitude of that risk, so much so that they believe “more studies should be conducted for controlling the period of pill use.”

But this study would seem to indicate that the safest “period of pill use” is no period at all.